Smoke rises after a bomb blast at a bus terminal in Jos, Nigeria, Tuesday, May 20, 2014. Two explosions ripped through a bustling bus terminal and market frequented by thousands of people in Nigeria's central city of Jos on Tuesday afternoon, and police said there are an unknown number of casualties. The blasts could be heard miles away and clouds of black smoke rose above the city as firefighters and rescue workers struggled to reach the area as thousands of people fled. (AP Photo/Stefanos Foundation)

Two car bombs exploded at a bustling bus terminal and market in Nigeria's central city of Jos on Tuesday, killing at least 118 people and wounding dozens.

There was no immediate claim of responsibility for the bombs, but they bore the hallmarks of Boko Haram, the Islamic extremist group that abducted nearly 300 schoolgirls last month.

The second blast came half an hour after the first, killing some of the rescue workers who had rushed to the scene, which was obscured by billows of black smoke.

Dozens of bodies and body parts were covered in grain that had been loaded in the second car bomb, witnesses said. A Terminus Market official said he helped remove 50 casualties, most of them dead. He spoke on condition of anonymity because he is not allowed to give information to reporters.

"It's horrifying, terrible," said Mark Lipdo of the Stefanos Foundation, a Christian charity based in Jos, who said he could smell burning human flesh.

Tensions have been rising between Christians and Muslims in Jos, the capital of Plateau state in Nigeria's Middle Belt region, which divides the country into the predominantly Muslim north and Christian south. It is a flash point for religious violence.

Boko Haram has claimed other recent bomb attacks, including two in April that killed more than 120 people and wounded more than 200 in Abuja, the nation's capital. One bomb went off at a busy bus station.

A suicide car bomber killed 25 people in northern Kano city on Monday. Police there detonated a second car bomb Monday. They said both would have killed many people, but the first exploded before it reached its target of restaurants and bars in the Christian quarter of the Muslim city.

Boko Haram, whose name means "Western education is sinful," has targeted schools, as well as churches, mosques, marketplaces, bus terminals and other spots where large numbers of civilians gather, in its campaign to turn Nigeria into an Islamic state. Half of Nigeria's population of 170 million is Christian, as is most of the population of Jos. The militants have increased the reach of their attacks this year, and their deadliness.